The present invention relates to soap curd dispersants which can be added in the rinse cycle or with the soap in the washing step.
The oldest, best known, and by far the most important surface active agents are soaps. The salient disadvantage of the soaps is their instability toward heavy-metal ions, particularly the calcium and magnesium found in hard water, as the calcium and magnesium salts of the fatty acids are quite insoluble in water. Soap, however, has at least two major points of superiority, i.e., low cost and high detergent powers in most of the cleaning operations encountered practically.
Fatty acid soaps in moderately hard water are known to provide excellent soil removal and very good suspension of soil in the wash cycle of laundering. However, in the subsequent step of rinsing, a smaller amount of residual soap, which cannot be totally extracted from the laundry items, comes in contact with a relatively large amount of hard water cations. This rinsing step can reprecipitate lime soap, carrying with it small but ultimately visible amounts of insoluble dirt and other "color bodies".